Thanks, Lenny. I just realised, actually, this is probably because of exams again - they're two months away, and this is when I normally start revising. And it's when I'm studying that I find it hardest to keep my hands away from my head.

I guess if this is the reason, though, at least I know that I've made it through a few sets of exams without it, so maybe I'll be able to manage this one too. *crosses fingers*